std.container.RedBlackTree versus C++ std::set

[Steven Schveighoffer]

On Thu, 14 Feb 2013 13:45:30 -0500, Rob T <alanb at ucora.com> wrote:

> When I look at the std.container source code, it seems that the payload  
> element is passed by value multiple times unnecessarily, so to minimize  
> copy construction you'll have to implement element as a class and  
> implement a dup function for it.
>
> I expect performance will increase substantially even with the extra  
> heap allocations.
>
> Alternatively, you can implement your own version of RedBlackTree with  
> pass by ref optimizations for insertion of struct elements.

If it was pass by ref, then rbt.insert(5) would not work.  And in fact, I  
wouldn't want things passed by ref if the element is int.  I have to  
admit, I did not consider expensive postblits when I designed it.  Almost  
all my testing is with integer types.

Unfortunately, D is in this state where taking a ref parameter means  
strictly lvalue.  So passing rvalues will not work.  D does not have the  
notion that C++ has where const type& can accept both rvalue and lvalue.   
We desperately need something similar.

-Steve